1
|
Gautam T, Kim E, Ng L, Choudhary V, Lima Amorim J, Loebel Roson M, Zhao R. Photooxidation-Initiated Aqueous-Phase Formation of Organic Peroxides: Delving into Formation Mechanisms. Environ Sci Technol 2024; 58:6564-6574. [PMID: 38578220 DOI: 10.1021/acs.est.3c01162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/06/2024]
Abstract
Formation of highly oxygenated molecules (HOMs) such as organic peroxides (ROOR, ROOH, and H2O2) is known to degrade food and organic matter. Gas-phase unimolecular autoxidation and bimolecular RO2 + HO2/RO2 reactions are prominently renowned mechanisms associated with the formation of peroxides. However, the reaction pathways and conditions favoring the generation of peroxides in the aqueous phase need to be evaluated. Here, we identified bulk aqueous-phase ROOHs in varying organic precursors, including a laboratory model compound and monoterpene oxidation products. Our results show that formation of ROOHs is suppressed at enhanced oxidant concentrations but exhibits complex trends at elevated precursor concentrations. Furthermore, we observed an exponential increase in the yield of ROOHs when UV light with longer wavelengths was used in the experiment, comparing UVA, UVB, and UVC. Water-soluble organic compounds represent a significant fraction of ambient cloud-water components (up to 500 μM). Thus, the reaction pathways facilitating the formation of HOMs (i.e., ROOHs) during the aqueous-phase oxidation of water-soluble species add to the climate and health burden of atmospheric particulate matter.
Collapse
Affiliation(s)
- Tania Gautam
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
| | - Erica Kim
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
| | - Lisa Ng
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
| | - Vikram Choudhary
- Air Pollution Exposure Laboratory, Division of Respiratory Medicine, Department of Medicine, Vancouver Coastal Health Research Institute, The University of British Columbia, Vancouver, British Columbia V5Z1W9, Canada
| | - Jessica Lima Amorim
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
| | - Max Loebel Roson
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
| | - Ran Zhao
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
| |
Collapse
|
2
|
Zhang W, Issa K, Tang T, Zhang H. Role of Hydroperoxyl Radicals in Heterogeneous Oxidation of Oxygenated Organic Aerosols. Environ Sci Technol 2024; 58:4727-4736. [PMID: 38411392 DOI: 10.1021/acs.est.3c09024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/28/2024]
Abstract
Heterogeneous oxidative aging of organic aerosols (OA) occurs ubiquitously in the atmosphere, initiated by oxidants, such as the hydroxyl radicals (•OH). Hydroperoxyl radicals (HO2•) are also an important oxidant in the troposphere, and its gas-phase chemistry has been well studied. However, the role of HO2• in heterogeneous OA oxidation remains elusive. Here, we carry out •OH-initiated heterogeneous oxidation of several OA model systems under different HO2• conditions in a flow tube reactor and characterize the molecular oxidation products using a suite of mass spectrometry instrumentation. By using hydrogen-deuterium exchange (HDX) with thermal desorption iodide-adduct chemical ionization mass spectrometry, we provide direct observation of organic hydroperoxide (ROOH) formation from heterogeneous HO2• and peroxy radicals (RO2•) reactions for the first time. The ROOH may contribute substantially to the oxidation products, varied with the parent OA chemical structure. Furthermore, by regulating RO2• reaction pathways, HO2• also greatly influence the overall composition of the oxidized OA. Last, we suggest that the RO2• + HO2• reactions readily occur at the OA particle interface rather than in the particle bulk. These findings provide new mechanistic insights into the heterogeneous OA oxidation chemistry and help fill the critical knowledge gap in understanding atmospheric OA oxidative aging.
Collapse
Affiliation(s)
- Wen Zhang
- Department of Chemistry, University of California, Riverside, California 92507, United States
| | - Kassem Issa
- Department of Evolution, Ecology, and Organismal Biology, University of California, Riverside, California 92507, United States
| | - Tiffany Tang
- Department of Chemistry, University of California, Riverside, California 92507, United States
| | - Haofei Zhang
- Department of Chemistry, University of California, Riverside, California 92507, United States
| |
Collapse
|
3
|
Wu Y, Kang J, Gao W, Bi M, Yang D, Ji R, Meng Q, Ma C. A DFT and kinetic study: Is it possible to prepare epoxides without catalysts using the in-situ generated peroxy radicals or peroxides by one-step method? J Comput Chem 2023. [PMID: 37283494 DOI: 10.1002/jcc.27172] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Revised: 05/11/2023] [Accepted: 05/24/2023] [Indexed: 06/08/2023]
Abstract
DFT calculations and kinetic analysis have been employed to comprehensively explore the possibility to prepare epoxides by one-step method using the in-situ generated peroxy radicals or hydroperoxides as epoxidizing agents. Computational studies demonstrated that the selectivities for the reaction systems of O2 /R2/R1, O2 /CuH/R1, O2 /CuH/styrene, O2 /AcH/R1 were 68.2%, 69.6%, 100% and 93.3%, respectively. The in-situ generated peroxide radicals, such as HOO˙, CuOO˙ and AcOO˙, could react with R1 or styrene by attacking the CC double bond to form a CO bond and subsequently undergoing a cleavage of OO bond to yield epoxides. Peroxide radicals could abstract a hydrogen atom from methyl group on R1, forming unwanted by-products. It should be noted that the hydrogen atoms of HOO˙ is easy to be abstracted by CC double bond and simultaneously the oxygen atom is connected to the CH moiety to form an alkyl peroxy radical (Rad11), greatly limiting the selectivity. The comprehensive mechanistic studies provide a deep understanding on preparing epoxides by one-step method.
Collapse
Affiliation(s)
- Yufeng Wu
- School of Chemical Engineering, Dalian University of Technology, Dalian, Liaoning, China
| | - Jiajie Kang
- School of Chemical Engineering, Dalian University of Technology, Dalian, Liaoning, China
| | - Wei Gao
- School of Chemical Engineering, Dalian University of Technology, Dalian, Liaoning, China
| | - Mingshu Bi
- School of Chemical Engineering, Dalian University of Technology, Dalian, Liaoning, China
| | - Dongcheng Yang
- School of Chemical Engineering, Dalian University of Technology, Dalian, Liaoning, China
| | - Runlai Ji
- School of Chemical Engineering, Dalian University of Technology, Dalian, Liaoning, China
| | - Qingwei Meng
- School of Chemical Engineering, Dalian University of Technology, Dalian, Liaoning, China
| | - Cunfei Ma
- School of Chemical Engineering, Dalian University of Technology, Dalian, Liaoning, China
| |
Collapse
|
4
|
Zhang W, Zhao Z, Shen C, Zhang H. Unexpectedly Efficient Aging of Organic Aerosols Mediated by Autoxidation. Environ Sci Technol 2023; 57:6965-6974. [PMID: 37083304 DOI: 10.1021/acs.est.2c09773] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Multiphase oxidative aging is a ubiquitous process for atmospheric organic aerosols (OA). But its kinetics was often found to be slow in previous laboratory studies where high hydroxyl radical concentrations ([•OH]) were used. In this study, we performed heterogeneous oxidation experiments of several model OA systems under varied aging timescales and gas-phase [•OH]. Our results suggest that OA heterogeneous oxidation may be 2-3 orders of magnitude faster when [•OH] is decreased from typical laboratory flow tube conditions to atmospheric levels. Direct laboratory mass spectrometry measurements coupled with kinetic simulations suggest that an intermolecular autoxidation mechanism mediated by particle-phase peroxy radicals greatly accelerates OA oxidation, with enhanced formation of organic hydroperoxides, alcohols, and fragmentation products. With autoxidation, we estimate that the OA oxidation timescale in the atmosphere may be from less than a day to several days. Thus, OA oxidative aging can have greater atmospheric impacts than previously expected. Furthermore, our findings reveal the nature of heterogeneous aerosol oxidation chemistry in the atmosphere and help improve the understanding and prediction of atmospheric OA aging and composition evolution.
Collapse
Affiliation(s)
- Wen Zhang
- Department of Chemistry, University of California, Riverside, California 92507, United States
| | - Zixu Zhao
- Department of Chemistry, University of California, Riverside, California 92507, United States
| | - Chuanyang Shen
- Department of Chemistry, University of California, Riverside, California 92507, United States
| | - Haofei Zhang
- Department of Chemistry, University of California, Riverside, California 92507, United States
| |
Collapse
|
5
|
Hu Z, Di Q, Liu B, Li Y, He Y, Zhu Q, Xu Q, Dagaut P, Hansen N, Sarathy SM, Xing L, Truhlar DG, Wang Z. Elucidating the photodissociation fingerprint and quantifying the determination of organic hydroperoxides in gas-phase autoxidation. Proc Natl Acad Sci U S A 2023; 120:e2220131120. [PMID: 36848575 PMCID: PMC10013783 DOI: 10.1073/pnas.2220131120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2022] [Accepted: 01/12/2023] [Indexed: 03/01/2023] Open
Abstract
Hydroperoxides are formed in the atmospheric oxidation of volatile organic compounds, in the combustion autoxidation of fuel, in the cold environment of the interstellar medium, and also in some catalytic reactions. They play crucial roles in the formation and aging of secondary organic aerosols and in fuel autoignition. However, the concentration of organic hydroperoxides is seldom measured, and typical estimates have large uncertainties. In this work, we developed a mild and environmental-friendly method for the synthesis of alkyl hydroperoxides (ROOH) with various structures, and we systematically measured the absolute photoionization cross-sections (PICSs) of the ROOHs using synchrotron vacuum ultraviolet-photoionization mass spectrometry (SVUV-PIMS). A chemical titration method was combined with an SVUV-PIMS measurement to obtain the PICS of 4-hydroperoxy-2-pentanone, a typical molecule for combustion and atmospheric autoxidation ketohydroperoxides (KHPs). We found that organic hydroperoxide cations are largely dissociated by loss of OOH. This fingerprint was used for the identification and accurate quantification of the organic peroxides, and it can therefore be used to improve models for autoxidation chemistry. The synthesis method and photoionization dataset for organic hydroperoxides are useful for studying the chemistry of hydroperoxides and the reaction kinetics of the hydroperoxy radicals and for developing and evaluating kinetic models for the atmospheric autoxidation and combustion autoxidation of the organic compounds.
Collapse
Affiliation(s)
- Zhihong Hu
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui230029, P. R. China
| | - Qimei Di
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui230029, P. R. China
| | - Bingzhi Liu
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui230029, P. R. China
| | - Yanbo Li
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui230029, P. R. China
| | - Yunrui He
- Energy and Power Engineering Institute, Henan University of Science and Technology, Luoyang, Henan471003, China
| | - Qingbo Zhu
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui230029, P. R. China
| | - Qiang Xu
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui230029, P. R. China
| | - Philippe Dagaut
- CNRS, Institut National des Sciences de l’Ingénierie et des Systèmes, Institut de Combustion, Aérothermique, Réactivité et Environnement, Orléans45071, cedex 2, France
| | - Nils Hansen
- Combustion Research Facility, Sandia National Laboratories, Livermore, CA94551
| | - S. Mani Sarathy
- King Abdullah University of Science and Technology, Clean Combustion Research Center, Thuwal23955-6900, Saudi Arabia
| | - Lili Xing
- Energy and Power Engineering Institute, Henan University of Science and Technology, Luoyang, Henan471003, China
| | - Donald G. Truhlar
- Department of Chemistry, Chemical Theory Center, and Minnesota Supercomputing Institute, University of Minnesota, Minneapolis, MN55455-0431
| | - Zhandong Wang
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui230029, P. R. China
- State Key Laboratory of Fire Science, University of Science and Technology of China, Hefei, Anhui230026, P. R. China
| |
Collapse
|
6
|
Brownwood B, Turdziladze A, Hohaus T, Wu R, Mentel TF, Carlsson PTM, Tsiligiannis E, Hallquist M, Andres S, Hantschke L, Reimer D, Rohrer F, Tillmann R, Winter B, Liebmann J, Brown SS, Kiendler-Scharr A, Novelli A, Fuchs H, Fry JL. Gas-Particle Partitioning and SOA Yields of Organonitrate Products from NO 3-Initiated Oxidation of Isoprene under Varied Chemical Regimes. ACS Earth Space Chem 2021; 5:785-800. [PMID: 33889791 PMCID: PMC8054245 DOI: 10.1021/acsearthspacechem.0c00311] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Revised: 02/17/2021] [Accepted: 02/25/2021] [Indexed: 05/24/2023]
Abstract
Alkyl nitrate (AN) and secondary organic aerosol (SOA) from the reaction of nitrate radicals (NO3) with isoprene were observed in the Simulation of Atmospheric PHotochemistry In a large Reaction (SAPHIR) chamber during the NO3Isop campaign in August 2018. Based on 15 day-long experiments under various reaction conditions, we conclude that the reaction has a nominally unity molar AN yield (observed range 90 ± 40%) and an SOA mass yield of OA + organic nitrate aerosol of 13-15% (with ∼50 μg m-3 inorganic seed aerosol and 2-5 μg m-3 total organic aerosol). Isoprene (5-25 ppb) and oxidant (typically ∼100 ppb O3 and 5-25 ppb NO2) concentrations and aerosol composition (inorganic and organic coating) were varied while remaining close to ambient conditions, producing similar AN and SOA yields under all regimes. We observe the formation of dinitrates upon oxidation of the second double bond only once the isoprene precursor is fully consumed. We determine the bulk partitioning coefficient for ANs (K p ∼ 10-3 m3 μg-1), indicating an average volatility corresponding to a C5 hydroxy hydroperoxy nitrate.
Collapse
Affiliation(s)
- Bellamy Brownwood
- Chemistry
Department and Environmental Studies Program, Reed College, Portland, Oregon 97202, United
States
| | - Avtandil Turdziladze
- Institute
for Energy and Climate (IEK-8), Forschungszentrum Jülich, Jülich 52428, Germany
| | - Thorsten Hohaus
- Institute
for Energy and Climate (IEK-8), Forschungszentrum Jülich, Jülich 52428, Germany
| | - Rongrong Wu
- Institute
for Energy and Climate (IEK-8), Forschungszentrum Jülich, Jülich 52428, Germany
| | - Thomas F. Mentel
- Institute
for Energy and Climate (IEK-8), Forschungszentrum Jülich, Jülich 52428, Germany
| | - Philip T. M. Carlsson
- Institute
for Energy and Climate (IEK-8), Forschungszentrum Jülich, Jülich 52428, Germany
| | | | - Mattias Hallquist
- Department
of Chemistry and Molecular Biology, University
of Gothenburg, Gothenburg 405 30, Sweden
| | - Stefanie Andres
- Institute
for Energy and Climate (IEK-8), Forschungszentrum Jülich, Jülich 52428, Germany
| | - Luisa Hantschke
- Institute
for Energy and Climate (IEK-8), Forschungszentrum Jülich, Jülich 52428, Germany
| | - David Reimer
- Institute
for Energy and Climate (IEK-8), Forschungszentrum Jülich, Jülich 52428, Germany
| | - Franz Rohrer
- Institute
for Energy and Climate (IEK-8), Forschungszentrum Jülich, Jülich 52428, Germany
| | - Ralf Tillmann
- Institute
for Energy and Climate (IEK-8), Forschungszentrum Jülich, Jülich 52428, Germany
| | - Benjamin Winter
- Institute
for Energy and Climate (IEK-8), Forschungszentrum Jülich, Jülich 52428, Germany
| | - Jonathan Liebmann
- Atmospheric
Chemistry Department, Max Planck Institute
for Chemistry, Mainz 55128, Germany
| | - Steven S. Brown
- Chemical
Sciences Division, Earth System Research Laboratory, NOAA, Boulder, Colorado 80305, United
States
| | - Astrid Kiendler-Scharr
- Institute
for Energy and Climate (IEK-8), Forschungszentrum Jülich, Jülich 52428, Germany
| | - Anna Novelli
- Institute
for Energy and Climate (IEK-8), Forschungszentrum Jülich, Jülich 52428, Germany
| | - Hendrik Fuchs
- Institute
for Energy and Climate (IEK-8), Forschungszentrum Jülich, Jülich 52428, Germany
| | - Juliane L. Fry
- Chemistry
Department and Environmental Studies Program, Reed College, Portland, Oregon 97202, United
States
| |
Collapse
|
7
|
Wagner JP. An Intramolecular Hydrogen-Shift in a Peroxy Radical at Cryogenic Temperatures: The Reaction of 2-Hydroxyphenyl Radical with O 2. Chemistry 2020; 26:12119-12124. [PMID: 32427391 DOI: 10.1002/chem.202000980] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Indexed: 11/08/2022]
Abstract
Peroxy radical hydrogen-shifts are pivotal elementary reaction steps in the oxidation of small hydrocarbons in autoignition and the lower atmosphere. Although these reactions are typically associated with a substantial barrier, we demonstrate that the [1,5]H-shift in the peroxy species derived from the 2-hydroxyphenyl radical 1 is so facile that it even proceeds rapidly in an argon matrix at 35 K through a proton-coupled electron transfer mechanism. Hydrogen-bound complexes of o-benzoquinone are identified as the main reaction products by infrared spectroscopy although their formation through O-O bond scission is hampered by a barrier of 11.9 kcal mol-1 at the ROCCSD(T)/cc-pVTZ/UB3LYP/6-311G(d,p) level of theory.
Collapse
Affiliation(s)
- J Philipp Wagner
- Institut für Organische Chemie, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 18, 72076, Tübingen, Germany
| |
Collapse
|
8
|
Lu B, Song C, Liu J, Trabelsi T, Francisco JS, Wang L, Zeng X. Dihalogenated Methyl peroxy Radicals: Spectroscopic Characterization and Photodecomposition by Release of HO .. Chemistry 2020; 26:2817-2820. [PMID: 31899574 DOI: 10.1002/chem.201905858] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2019] [Indexed: 11/08/2022]
Abstract
Two atmospherically relevant dihalogenated methylperoxy radicals CHX2 OO. (X=F and Cl) have been generated through O2 -oxidation of the corresponding alkyl radicals CHX2 . in the gas phase. The IR spectroscopic characterization of both radicals in cryogenic Ar- and N2 -matrices (15 K) is supported by 18 O-labeling and ab initio calculations at the UCCSD(T)/aug-cc-pVTZ level. Upon 266 nm laser irradiation, both radicals decompose mainly by releasing hydroxyl radicals (→HO. +X2 CO) via the intermediacy of intriguing α-hydroperoxyalkyl radicals (. CX2 OOH), implying that the photooxidation of dihalogenated hydrocarbons might serve as important sources of HO. radicals in the atmosphere.
Collapse
Affiliation(s)
- Bo Lu
- College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123, P. R. China
| | - Chao Song
- College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123, P. R. China
| | - Jie Liu
- College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123, P. R. China
| | - Tarek Trabelsi
- Department of Earth and Environmental Science and Department of, Chemistry, University of Pennsylvania, Pennsylvania, 19104, USA
| | - Joseph S Francisco
- Department of Earth and Environmental Science and Department of, Chemistry, University of Pennsylvania, Pennsylvania, 19104, USA
| | - Lina Wang
- Department of Chemistry, Fudan University, Shanghai, 200433, P. R. China
| | - Xiaoqing Zeng
- College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123, P. R. China.,Department of Chemistry, Fudan University, Shanghai, 200433, P. R. China
| |
Collapse
|
9
|
Nozière B, Vereecken L. Direct Observation of Aliphatic Peroxy Radical Autoxidation and Water Effects: An Experimental and Theoretical Study. Angew Chem Int Ed Engl 2019; 58:13976-13982. [PMID: 31361086 DOI: 10.1002/anie.201907981] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Indexed: 11/08/2022]
Abstract
The autoxidation of organic peroxy radicals (RO2 ) into hydroperoxy-alkyl radicals (QOOH), then hydroperoxy-peroxy radicals (HOOQO2 ) is now considered to be important in the Earth's atmosphere. To avoid mechanistic uncertainties these reactions are best studied by monitoring the radicals. But for the volatile and aliphatic RO2 radicals playing key roles in the atmosphere this has long been an instrumental challenge. This work reports the first study of the autoxidation of aliphatic RO2 radicals and is based on monitoring RO2 and HOOQO2 radicals. The rate coefficients, kiso (s-1 ), were determined both experimentally and theoretically using MC-TST kinetic theory based on CCSD(T)//M06-2X quantum chemical methodologies. The results were in excellent agreement and confirmed that the first H-migration is strongly rate-limiting in the oxidation of non-oxygenated volatile organic compounds (VOCs). At higher relative humidity (2-30 %) water complexes were evidenced for HOOQO2 radicals, which could be an important fate for HOO-substituted RO2 radicals in the atmosphere.
Collapse
Affiliation(s)
- Barbara Nozière
- IRCELYON, CNRS, Université Claude Bernard Lyon 1, 2 avenue Albert Einstein, 69626, Villeurbanne, France
| | - Luc Vereecken
- Forschungszentrum Jülich GmbH, 52425, Jülich, Germany
| |
Collapse
|
10
|
Zhao Y, Thornton JA, Pye HOT. Quantitative constraints on autoxidation and dimer formation from direct probing of monoterpene-derived peroxy radical chemistry. Proc Natl Acad Sci U S A 2018; 115:12142-7. [PMID: 30413618 DOI: 10.1073/pnas.1812147115] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Organic peroxy radicals (RO2) are key intermediates in the atmospheric degradation of organic matter and fuel combustion, but to date, few direct studies of specific RO2 in complex reaction systems exist, leading to large gaps in our understanding of their fate. We show, using direct, speciated measurements of a suite of RO2 and gas-phase dimers from O3-initiated oxidation of α-pinene, that ∼150 gaseous dimers (C16-20H24-34O4-13) are primarily formed through RO2 cross-reactions, with a typical rate constant of 0.75-2 × 10-12 cm3 molecule-1 s-1 and a lower-limit dimer formation branching ratio of 4%. These findings imply a gaseous dimer yield that varies strongly with nitric oxide (NO) concentrations, of at least 0.2-2.5% by mole (0.5-6.6% by mass) for conditions typical of forested regions with low to moderate anthropogenic influence (i.e., ≤50-parts per trillion NO). Given their very low volatility, the gaseous C16-20 dimers provide a potentially important organic medium for initial particle formation, and alone can explain 5-60% of α-pinene secondary organic aerosol mass yields measured at atmospherically relevant particle mass loadings. The responses of RO2, dimers, and highly oxygenated multifunctional compounds (HOM) to reacted α-pinene concentration and NO imply that an average ∼20% of primary α-pinene RO2 from OH reaction and 10% from ozonolysis autoxidize at 3-10 s-1 and ≥1 s-1, respectively, confirming both oxidation pathways produce HOM efficiently, even at higher NO concentrations typical of urban areas. Thus, gas-phase dimer formation and RO2 autoxidation are ubiquitous sources of low-volatility organic compounds capable of driving atmospheric particle formation and growth.
Collapse
|
11
|
Abstract
Atmospheric chemistry is an important discipline for understanding air pollution and its impacts. This mini-review gives a brief history of air pollution and presents an overview of some of the basic photochemistry involved in the production of ozone and other oxidants in the atmosphere. Urban air quality issues are reviewed with a specific focus on ozone and other oxidants, primary and secondary aerosols, alternative fuels, and the potential for chlorine releases to amplify oxidant chemistry in industrial areas. Regional air pollution issues such as acid rain, long-range transport of aerosols and visibility loss, and the connections of aerosols to ozone and peroxyacetyl nitrate chemistry are examined. Finally, the potential impacts of air pollutants on the global-scale radiative balances of gases and aerosols are discussed briefly.
Collapse
Affiliation(s)
- Jeffrey S Gaffney
- Environmental Research Division, Argonne National Laboratory, 9700 South Cass Avenue, Building 203, Argonne, IL 60439-4843, USA.
| | | |
Collapse
|
12
|
Abstract
Many reactive oxygen species such as ozone, singlet oxygen, hydroxyl radical, and organic oxyradicals have been implicated in damage to plant organs and biopolymers such as chloroplasts, cell membranes, proteins, and DNA. The principal defenses against these reactive molecules and free radicals in plants include detoxifying enzymes (catalase, superoxide dismutase, etc.) and also lower molecular weight secondary products with antioxidant activity. These latter compounds include a great variety of phenolic compounds, carotenoids, nitrogenous, and sulfur-containing materials. Some of the more important mechanisms of action of the secondary compounds will be discussed, with emphasis on the use of structural and kinetic data to identify the most effective antioxidants against peroxy radical-induced damage, which is perhaps the most important of the oxidative stresses present in the usual environment of plants. © 1995 Wiley-Liss, Inc.
Collapse
Affiliation(s)
- Richard A Larson
- Institute for Environmental Studies, University of Illinois at Urbana-Champaign, Urbana, Illinois
| |
Collapse
|